Rust is a common problem in plumbing. Oxidation can eat away at metal pipes and possibly result in a leak. Regular maintenance can help prevent rust from building up inside a pipe, but this requires removal of the pipe for cleaning. Removing rust scaling from inside pipes requires some basic tools and cleaning chemicals.
Turn off the water going to the pipe and unscrew the pipe with a wrench so you can access the inside. Place a container under the pipe to collect any water that comes out of the pipe as you remove it.
Mix a rust and scale removal chemical with water in a container as recommended by the instructions. Some chemicals will not require diluting while others recommend adding water prior to use. Wear rubber gloves to prevent skin exposure.
Submerge the pipe in the rust removal solution for at least 15 minutes to allow the solution time to soak into the rust on the inside of the pipe. Wait longer if recommended.
Insert a metal pipe cleaning brush in the pipe and vigorously move it in and out of the pipe to scrape away rust.
Continue submerging and scraping the pipe until the rust and scale deposits are removed from the inside of the pipe. Reattach the pipe and turn the water valve back on.